(a) Field of the Invention
The present invention relates to a power train of an automatic transmission. More particularly, the present invention relates to a power train of an automatic transmission that realizes six forward speeds and one reverse speed.
(b) Description of the Related Art
A typical shift mechanism of an automatic transmission utilizes a combination of planetary gear sets. A power train of such an automatic transmission changes rotating speed and torque received from a torque converter of the automatic transmission, and accordingly changes and transmits the torque to an output shaft.
When a transmission includes a relatively large number of shift speeds, speed ratios can be optimally designed and therefore a vehicle can have better fuel mileage and better performance than those with smaller numbers of shift speeds.
In addition, features of a power train such as durability, efficiency in power transmission, and size depend a lot on the layout of combined planetary gear sets.
A manual transmission with many speeds causes the inconvenience of excessively frequent shifting by the driver. Therefore, a transmission with more shift-speeds lends itself better to automatic transmissions.
Korean Patent No. 0504520 discloses a power train of an automatic transmission with six forward speeds and one reverse speed. The transmission includes three planetary gear sets, two clutches, and three brakes. However, since three planetary gear sets are used, the power train is heavy.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.